As your account's admin you are able to manage your account's users: add, edit and delete them. How do you do that? Let's begin.
In the "Management" > "Users" you can
- check the total number of your account's user seats and how many of them are occupied
- check how users are attached to different sites/projects
- edit user's information
- add and remove the sites user can see and use.
1. First you have to check if there are enough of seats for new users. In this case there are 26 users and 80 user seats. So 54 seats are still unused and available.
Adding new users is easy. Start by following this link: Add new users.
2. You can check how users are attached to different sites or projects in your domain.
In the field "Sites" open the the domain tree behind the yellow button, select the site(s) you want to check, press "Choose" and on the next page "Search", and you'll get to see which of the users are attached to the site(s) you selected from the domain tree.
3. If you need to edit user information, move the cursor above the wanted user and click to open.
4. If you want to add or remove sites from some user, go to that user's information and open the "Sites" selection. You get to see all of the sites in your organisation's domain tree. You can select now the sites this specific user needs to have access to.
Notice also that the person can be the responsibility party for a site only if (s)he has access to that specific site.